The coefficient of thermal expansion of a thermosetting organic material is about 50 to 80 ppm/° C. and it is significant higher several to tens times than the CTE of a inorganic particles, that is ceramic material, or a metal, (for example, the CTE of silicon is 3 to 5 ppm/° C., while the CTE of copper is 17 ppm/° C.). Thus, when a thermosetting material is used together with an inorganic material or a metal in the fields of a semiconductor, a display, or the like, the properties and processability of a polymer material may be significantly limited due to the CTE-mismatch of the thermosetting material and the inorganic material or the metal. In addition, in a semiconductor packaging where a silicon wafer is adjacent to epoxy substrate or coated film in which an inorganic barrier layer is coated on the a polymer film to impart gas barrier properties, product defects such as crack formation in an inorganic layer, the warpage of a substrate, the peeling-off of a coating layer, the failure of a substrate, and the like, may occur due to a significant CTE-mismatch between constituent elements upon the changes of processing and/or service temperatures.
Because of the high CTE of the thermosetting material and the consequently the high dimensional change of the thermosetting material, the developments of next generation semiconductor substrates, printed circuit boards (PCBs), packaging, organic thin film transistors (OTFTs), and flexible display substrates and so on may be limited. Particularly, the current semiconductor and PCB industries have difficulties in the design, processing and securing of the reliability of the next generation components requiring high degrees of integration, miniaturization, flexibility, performance and so on, due to the epoxy materials with the much higher CTE than metal/ceramic materials. In other words, due to the high thermal expansion properties of the epoxy material at component processing temperatures, defects may be generated, processability may be limited, and the design of components and the securing of processability and reliability therein may be in difficulties. Accordingly, improved thermal expansion properties, that is dimensional stability of the epoxy are required in order to secure processability and reliability in electronic components.
In general, the making a composite of the epoxy compound with inorganic particles (an inorganic filler) and/or fibers has been used extensively, in order to improve thermal expansion properties (i.e., to obtain a low CTE) in a thermosetting epoxy compound. When the composite of the epoxy compound and the inorganic particles as the filler are formed in order to improve thermal expansion properties, a large amount of inorganic silica particles with a diameter of about 2 to 30 μm is required to be used to obtain a decreasing effect of CTE. However, due to the filling of the large amount of inorganic particles, the processability and physical properties of the parts may be deteriorated. That is, the presence of the large amount of inorganic particles may decrease fluidity, and voids may be generated during the filling of narrow spaces. In addition, the viscosity of the material may increase exponentially with the addition of the inorganic particles. Further, with the miniaturization of semiconductor structure, the decrease in fluidity (viscosity reduction) may be worsened since the size of the inorganic particles tends to decrease and the filler with a particle size of 1 μm or less is used. When inorganic particles with a large average diameter are used, the frequency of insufficient filling of a composition including a resin and the inorganic particles may increase. Even though the CTE may be largely decreased when a composition including an organic resin and a fiber as the filler is used, the CTE of composition may be still higher as compared to that of a silicon chip or the like.
As described above, the manufacturing of highly integrated and high performance electronic parts for next generation semiconductor substrates, PCBs, and the like may be restricted due to the limitations in the composite technology of the current epoxy compounds. Thus, the development of a novel compound having improved heat resistance properties—namely, a low CTE and Tg-less—is required to overcome a high CTE and consequently the insufficient thermal properties and processability of a common thermosetting polymer composite.